Effects of alpha-adrenergic stimulation on the sarcolemmal Na+/Ca(2+)-exchanger in adult rat ventricular cardiocytes.
OBJECTIVE
The cardiac sarcolemmal Na+/Ca(2+)-exchanger (NCX) plays an important role in the maintenance of the myocardial Ca2+ homeostasis which is altered in cardiac hypertrophy and failure. The aim of the present study was to investigate whether alpha-adrenergic stimulation known to induce cardiac hypertrophy might be involved in the regulation of the sarcolemmal NCX.


METHODS
Adult rat ventricular cardiocytes (ARC) were isolated from male Sprague-Dawley rats. Phenylephrine, an alpha-adrenergic agonist, was used as hypertrophic agent. NCX expression was measured by competitive RT-PCR and Western blot analysis.


RESULTS
alpha-Adrenergic stimulation of ARC with 10 microM phenylephrine for 24 h resulted in a significant increase of the NCX mRNA (2.5-fold) and the NCX protein level (1.8-fold). The changes on the expression level were blocked by the alpha 1-adrenoceptor antagonist prazosin.


CONCLUSIONS
The data demonstrate that the NCX expression level is up-regulated by the activation of the alpha-adrenergic signal transduction pathway. The increased NCX mRNA level induced by alpha-adrenergic stimulation appeared to be translated into increased NCX protein level.
Reinecke
H
H
Universität Freiburg, Innere Medizin III, Kardiologie und Angiologie, Berlin-Buch, Germany. hreineck@u.washington.edu
Vetter
R
R
Drexler
H
H
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D011224:Prazosin / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012508:Sarcolemma / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger / Q000187:drug effects* / Q000235:genetics; D013268:Stimulation, Chemical
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D012333:RNA, Messenger; D019831:Sodium-Calcium Exchanger; D010656:Phenylephrine; D011224:Prazosin